58 MANUAL OF HUMAN PROTOZOA 



stained, the nuclei are much more clearly visible, and 

 glycogen bodies are stained reddish brown, while the 

 chromatoid body remains unstained. 



Permanent preparation 



Permanent preparations are employed to aid in identifi- 

 cation of living protozoa, and not as substitutes for fresh 

 preparations. Smears are made on cover-glasses, and not 

 on slides as in fresh preparations; mark with India ink, 

 wax pencil, etc., the unsmeared side of the covers. Instead 

 of trying to place all data, simply write the number, and 

 enter on a record card all necessary data, such as the name 

 of the person, date, condition of the specimen, fixative, 

 stain, and any other remarks. 



The smears should be left horizontallv with the smeared 

 side up for a short while. Place a jar above them to exclude 

 dust, flies, etc. The purpose of leaving the slide for a few 

 minutes is not to dry the smear, but to allow the active 

 trophozoites to become attached to the cover by pseudo- 

 podia or flagella and at the same time to allow the fluid 

 to evaporate a little. Smears made from dvsenteric or fluid 

 faeces should be fixed almost immediatelv, and those made 

 from diarrhoeic or formed faeces emulsified in warm salt 

 solution should be left for a few minutes. In any case, do 

 not let the smear dry, except a narrow peripheral zone. 



The smears are next to be fixed. For fixation, Schaudinn's 

 fixative is most widely used and advocated here exclu- 

 sively, though any good histological or cytological fixatives 

 will do. Schaudinn's fluid is made up as follows: Mercuric 

 chloride (HgCl, or corrosive sublimate) 6-7% (cold satu- 

 rated) aqueous solution 6 cc, 95% or absolute alcohol 3 cc. 



